Back To Basics; Why Foods of Wild Primates Have Relevance for Modern Human Health.

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Back To Basics; Why Foods of Wild Primates Have Relevance for Modern Human Health.

Katharine Milton PhD.

Many current health problems are attributed to diet, and numerous views exist as to which types of foods contribute to such problems. This issue is not one of purely academic interest—rather, it has important ramifications for human health and well-being in the new millennium. It is difficult to comment on "the best diet" for humans because there have been and are so many different yet successful diets in our species. Humans can thrive on diets consisting almost exclusively of the raw fat and protein of marine mammals (Arctic Eskimo) and on diets composed largely of a few wild plant species (Australian aborigines of the Western Desert); and there is an almost infinite number of successful dietary permutations between these two extremes. Because of the dietary diversity modern humans display, it is reasonable to conclude that human ancestors exhibited similar flexibility. Like extant wild primates, our ancestors were probably opportunistic foragers and took advantage of the most nutritious foods in their environment at any given time, so long as these could be secured without undue cost or hazard.

Present fossil evidence places the earliest human beings at approximately 2 million y ago. In contrast, evidence for agriculture has been dated to only some 12 000 y ago. This means for most of human existence, members of our genus (Homo) and species (Homo sapiens) have lived as hunter-gatherers, that is, people using only wild plants and animals as foods. Various attempts have been made to reconstruct the average daily macronutrient intake for paleolithic hunter-gatherers. The logic behind such attempts seems to be the belief that modern human biology is somehow adapted to paleolithic foodways and that, by following such a diet, we might be able to prevent many of the so-called diseases of civilization (e.g., cardiovascular disease, obesity, typeII diabetes).

However, data from ethnographic studies of recent (largely 20th century) hunter-gatherers and evidence from historical accounts and archaeologic sites indicate that past hunter-gatherer enjoyed a rich variety of different diets, depending on locale and season of the year. Thus, nutrient estimates for "the average paleolithic diet" probably do not reflect actual daily intakes for many hunter-gatherers. In fact, we do not know much about the range of foods our paleolithic ancestors ate each day or season in almost any environment, although it seems likely that periods of relative food abundance may have alternated with periods of low food availability in many environments.

Regardless of what paleolithic hunter-gatherers were eating, there is little evidence to suggest that human nutrient needs or digestive physiology were significantly affected by such diets at any point in human evolution. To date, we know of few adaptations to diet in the human species that differentiate us from our closest living relatives, the great apes. Those identified are largely (although not exclusively) regulatory mutations such as lactase synthesis in adulthood, and unique selective pressures favoring such diet-associated mutations seem fairly well understood.

Food has played a major role in human evolution but in a somewhat different way than seems generally appreciated. Humans are not creations sui generis. Rather, they have an evolutionary history as anthropoid primates that stretches back more than 25million y, a history that shaped human nutrient requirements and digestive physiology long before there were humans or even protohumans.
Hunter-gatherers were not free to determine their diet—quite the opposite; it was their predetermined need for particular nutrients that constrained their evolution. At the same time these dietary needs apparently allowed for natural selection to favor increased brain size in the human lineage and the concomitant development of technologic, social, and other abilities directed at securing these nutrients; in this sense, it can be said that diet influenced, indeed drove, human evolution.